Brake retractor resetting mechanism

ABSTRACT

A brake retractor assembly in which the automatic adjustment mechanism has a locking plate carried by a sleeve member surrounding the retractor rod and held in tilted locking position during brake retraction and in which the locking plate is automatically moved into unlocked position during brake actuation when the rod is moved beyond the normal brake release clearance distance. A return spring connection between the rod and sleeve member resets the rod automatically to its original position in the sleeve member upon movement of the locking plate to the unlocked position when the brake lining needs replacement.

United States Patent [72] Inventors C. Lucas Plant; [56] ReferencesCited [2]] A l N 3mg:- Li'm, Ohio UNITED STATES PATENTS pp o (22] FiledMayzhlgw 3.091310 5/l963 Smithetal 188/l96(P) [45] Patented May 25, 1971Primary Examiner-Duane A. Reger [73] Assignee The B. F. Goodrich CompanyAttorneys-John D. Haney and Harold S" Meyer New York, N.Y.

ABSTRACT: A brake retractor assembly in which the automatic adjustmentmechanism has a locking plate carried by a sleeve member surrounding theretractor rod and held in tilted [54] BRAKE RETRACTQR RESETTINGMECHANISM locking position during brake retraction and in which thelclmm 2 Drawmg locking plate is automatically moved into unlockedposition [52] U5. Cl 188/196, dur g b ake actuation when the rod ismoved beyond the nor- 188/71,}; mal brake release clearance distance. Areturn spring connec- [51] Int. Cl ..Fl6d 65/54, tion between the r anleev mem er res the r d au F16d 55/18 matically to its original positionin the sleeve member upon [50] Field of Search 188/795 mo emen of thelocking plate o he nlock posi i n wh n (or 71.7, s, 196 (P) the brakelining needs replacement.

PATENTEUHAYZSIQH 3,580,366

INVENT )R.S

C. LUCAS PLAAT DONALD F. LINN gm 2M 29.

.AT'T

BRAKE RETRACTOR RESETTING MECHANISM BACKGROUND OF THE INVENTION Thisinvention relates to mechanism for automatically maintaining a uniformrelease clearance (and therefore a uniform actuating stroke) for brakesand similar equipment. Mechanisms of this type are commonly used inbrake systems to compensate for wear of the brake linings and otherbrake parts and are popularly called automatic brake adjusters. Althoughthe present invention is explained here in connection with brakes, themechanism has utility in other environments where similarwear-compensation is needed such as in clutches.

As the brake linings and other parts wear, the adjusting mechanism ofthe brake retractor automatically moves the retractor rod to a positionwhich is extended to compensate for the wear. When the retractor rodreaches a certain position, this indicates that the brake lining needsto be replaced. Lining replacement has presented a serious servicingproblem because it has necessitated removal of the adjuster from thebrake to reset the retractor rod. It has also been necessary to usespecial tools and equipment because of the special design of theadjuster and retractor to fit in small spaces on an aircraft.Furthermore, it has been necessary to force the retractor rod back intothe retractor against the resistance of the locking plate. Thesedifficulties encountered-in the replacement of brake linings areespecially critical in servicing helicopter installations where spaceand weight limitations are historically critical. Another problem isthat the time and place of brake lining replacement is not predictablesince the wear is not the same for different types of braking. Thismeans that replacement of brake linings may have to be done anywhere andat any time. In the operation of aircraft for commercial, private ormilitary applications, time is of the essence and any delay caused byservicing is not only costly but seriously impairs the utility of theaircraft.

SUMMARY OF THE INVENTION In the retractor assembly of this invention, aretractor rod resetting mechanism is provided which returns the rod to aposition where the lining may be replaced without requiring removal ofthe adjuster from the brake, without having to force back the retractorrod against the latch and without having to use special tools andtime-consuming effort. The retractor assembly of this invention includesa heavy-duty locking mechanism in which the locking plate is locatedwhere there is space for a reinforced high strength construction. Thelocking plate is carried by a sleeve member which is movable axiallyupon actuation and retraction of the brake members. A housing membermounted in the brake torque frame surrounds the sleeve member and ahelical retractor spring is interposed between the sleeve and housing.The helical spring is preloaded and bears at one end against a washerseated in the housing and at the other end it bears against a washermounted on the sleeve member. The sleeve member has a flanged endadjacent the washer in the housing and this flange fits in a groove inone edge of the locking plate. Under the preloaded condition of theretractor spring a lip of the locking plate is held in aleverage-applying condition between the washer and sleeve flange. Thisleverage causes the locking plate to assume a tilted or canted positionin which the plate frictionally engages the retracting rod which isslidably mounted in the sleeve member.

When the brake is actuated, the locking plate remains in frictionalengagement with the rod and as the rod is pulled axially out of thehousing, the sleeve member travels with the rod a distance which doesnot exceed a preestablished limit corresponding to the allowable releaseclearance of the brake members. As a result of the wear of the brakefriction faces, however, the operating stroke of the rod increasesprogressively. Whenever the stroke of the rod exceeds the aforesaidpreestablished limit, the locking plate engages a stop member on thehousing which straightens the locking plate and automatically disengagesthe plate from the rod and therefore permits the rod to move freelyrelative to the locking plate and sleeve until the rod reaches aposition in which the brake is engaged.

On the release of the brake actuation system following any suchadjusting movement of the rod, reengagement of the locking plate on therod is effected so that the retraction motion of the sleeve and rod islimited to an amount necessary to maintain a uniform brake releaseclearance. This result is accomplished without varying the amplitude ofdeflection of the retractor spring itself. Owing to the fact that theretractor spring has a fixed deflection amplitude, the force required toactuate the brake also remains uniform throughout the life of the brake.

The retractor rod has a cylindrical chamber to accommodate a secondspring for resetting the rod. This resetting spring is compressedbetween a retainer ring at one end of the rod and a plate held in astationary position relative to the sleeve by a pin extendingthrough thehelical spring and mounted on the sleeve. The resetting spring iscompressed as the rod'is extended axially out of the sleeve duringadjusting movement of the rod relative to the sleeve. This compressionof the resetting spring continues during every adjustment of the rod forthe life of the brake linings.

When it comes time for replacing the lining the locking plate isstraightened as by inserting a screwdriver between the housing andlocking plate. This unlocks the plate from the rod and permits theresetting spring to return the rod to the starting position. The liningcarrier is then turned in a circumferential direction to disengage therod from the carrier and remove the carrier from the brake. A new liningcarrier is inserted in the brake and brought into engagement with theretractor rod. The brake is then ready for operation.

The accompanying drawings show one preferred form of resetting mechanismas applied to a mechanical ratchet-type brake retractor made inaccordance with and embodying this invention and which is representativeof how this invention may be practiced.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a longitudinal cross section of the retractor assemblyinstalled in a typical disc brake, the assembly being in the conditionits parts occupy when the brake is retracted or released, the retractorrod being shown with the upper half in the extended position and thelower half in the reset position, the brake parts being shown ingeneralized or somewhat schematic form with some parts being brokenaway;

FIG. 2 is a view on the line 2-2 of FIG. 1.

DETAILED DESCRIPTION A brake retractor of the general type describedhereinafter is the subject of a related patent application having thesame assignee as this application. A retractor assembly 10 is mountedrigidly in a torque frame 11 of a brake, the frame in turn being adaptedfor mounting to a vehicle structure (not shown). Frame 11 carries alining carrier 12 in parallel axial alignment with a rotatable disc 13.The latter is in splined engagement at its periphery with a rotarymember 14 which may be part of the wheel structure with which the brakeis associated. On the other side of the rotatable disc 13 in the areawhich is broken away, another lining carrier and retractor assembly likethat shown may be mounted on the torque frame 1 I.

To actuate the brake and engage the brake members, a hydraulic piston 15mounted in a cylinder I6 in the brake frame II is adapted fordisplacement in response to hydraulic pressure to urge lining carrier 12against the brake disc 13 which resists axial movement by engaging otherbrake memisli ers not shown. The brake members as shown in FIG. I are inThe brake retractor assembly includes a cylindrical housing 19 which maybe part of the brake frame 11 or adapted for tight anchorage inside thebrake frame as shown in FIG. 1. Extending axially of the housing 19 andcontained therein is an adjusting mechanism 21 which is supported forreciprocation within the housing. Adjusting mechanism 21 has a sleevemember 22 disposed in concentric relation to and within the cylindricalhousing 19. Interposed between the sleeve member 22- and the housing 19is a helical retractor spring 23. At the left end of the sleeve 22 (asviewed in FIG. 1) is a spring-retaining member such as washer 24extending from the sleeve radially outward to the inner surface ofhousing 19. The washer 24 engages one end of the retractor spring 23 andremoval from the housing 19 during operation is prevented by a retainingring 25 set in a groove in the housing 19 and engageable with the outerperiphery 26 of the washer.

At the inner periphery of the washer 24 another retaining ring 27 is setin a groove in the sleeve member 22 on the side of the washer oppositeto that in engagement with the retractor spring 23.

At the other end of the housing 19, a spring-retaining washer 32 isseated against a shoulder 33 of the housing and extends from the housingto the sleeve member 22 which is supported by and held in slidableengagement with the washer. The washer 32 serves as an anchorage for theother end of the retractor spring 23 which is compressed in a preloadedcondition between the washer 32 and washer 24.

The sleeve member 22 extends (to the right as shown in FIG. 1) axiallybeyond the washer 32 in the released condition of the brake and has aradially extending flange 34 spaced from the washer at the edge of thesleeve member.

A retractor rod 35 is held in slidable engagement within the sleevemember 22 and extends towards the braking members where it is connectedto the lining carrier 12 as by insertion of the enlarged head of theretractor rod 35 in a slot 36 of the lining carrier 12 as shown in FIG.1 or by other arrangements well known in the art.

A locking plate 37 which is ofa generally annular disc shape is disposedat the flanged end of the sleeve member 22 and has a central opening 33through which the rod 35 projects of slightly greater diameter than thediameter of the rod. The locking plate 37 has an axially extendingflange 39 which overlaps the flanged end of the sleeve member 22 at oneedge of the locking plate. The flange 39 has a radially inwardlyextending edge portion such as lip 41 which is disposed in the spacebetween the washer 32 and the flange 34 of the sleeve member 22. At thediametrically opposite edge of the locking plate 37, the flange 39 has ahousing engaging portion such as radially outwardly extending car 42which has a radius greater than the radius of a stop member such asinwardly extending flange 43 on the housing 19. This flange 43 and car42 are spaced apart a predetermined distance indicated by letter X shownin FIG. 1. An opening 44 in the housing 19 is provided through which theear 42 may extend.

The rod 35 has acylindrical chamber to accommodate a resilient helicalresetting spring 45 which is mounted in compression within the retractorrod with one end pressed against a plate 46 connected to the sleevemember 22 by a pin 47 which is held in a bushing 48 of the sleeve memberas by threaded engagement of nut 49 on the end of the pin which extendsthrough the bushing. The other end of the resetting spring 45 is pressedagainst a washer 51 held by a retaining ring 52in a groove at the innerface of the cylindrical chamber of the retractor rod 35 In the releasedcondition of the brake, the flange 34 of the sleeve member 22 under thebias of retractor spring 23 acting on washer 24 presses the lip 41 ofthe locking plate 37 against the washer 32 to provide a positiveretracted position for the retracting rod 35. The surface of the lip 41which abuts the washer 32 is tapered outwardly and away from the surfaceof the washer and this plus the configuration shown in FIG. 1 of thelocking plate 37 and flange 39 insures that the locking plate remainstilted and in engagement with the retracting rod when the rod is in aretracted position as shown in FIG. 1. The flange 39 except for ear 42,has a radius less than the radius of the housing flange 43 so that timay slide past the flange 43 when the rod 35 is reciprocated. The flange43 is adapted to engage the ear 42 of the locking plate 37 only when therod 35 is advanced rightward (as shown in FIG. 1) a distance sufficientto bring the car 42 against the flange 43.

When the brake is operated by communicating hydraulic fluid to piston 15the latter displaces the lining carrier 12 rightward (as shown inFIG. 1) pulling rod 35 axially through the flange 43 of housing 19.Locking plate 37 moves rightward as the rod advances because of thetilting position of the locking plate which keeps it in tight frictionalengagement with the rod 35. Should there be no appreciable wear or othercondition materially changing the release clearance between the brakingmembers while these members are engaged, then rod 35 will not be axiallydisplaced an amount sufiicient to bring ear 42 of the locking plate 37against the flange 43. Instead locking plate 37 will remain in africtionally engaged position with the rod 35 When the brake actuationpressure is released, the retractor spring 23 will expand to return therod 35 to its original starting position. The mechanism is designed sothat the distance designated by dimension X in FIG. 1 between theannular flange 43 and the released position of the car 42 on the lockingplate 37 is equal to the maximum allowable release clearance between thebraking members. So long as the release clearance does not exceed anamount indicated by dimension X the locking ring 37 will always remainin tight frictional engagement with rod 35 and the brake members may beengaged and released repeatedly.

Owing to the erosion of the brake members and the brake linings as thebrake is used, the release clearance between the lining carrier 12,brake disc 13 and the other brake members tends to increaseprogressively. The existence of this condition is automatically sensedin this mechanism because rod 35 and lining carrier 12 can be displacedfor whatever distance necessary to bring about brake engagementregardless of wear. Accordingly, whenever the lining carrier 12 and rod35 are moved through a distance greater than that equal to dimension Xin order to engage the brake members, the ear 42 of locking plate 37will be forced into engagement with flange 43. The flange 43 then urgesthe locking plate 37 into the position in which the radially extendingface is straightened to a position where the frictional engagement ofthe locking plate with rod 35 is reduced. Rod 35 can then be movedthrough the locking plate 37 and the effective length increased bywhatever distance it is required to maintain brake engagement. Referringto FIG. 1, the extended position of rod 35 in the worn condition of thebrake is illustrated by the upper half of rod 35 and the originaleffective length of rod 35 with the brake in the new or unwom conditionis illustrated by the lower half of the rod.

On the subsequent release of fluid pressure against the piston 15, theretraction forces on the brake members will act to move rod 35 in thereverse direction and the biasing force of the retractor spring 23against the sleeve member 22 carrying flange 34 in engagement with lip41 of the locking plate is effective to tilt the locking plate 37 into africtionally engaged locking position on rod 35. Accordingly, theretractor spring 23 will then through the agency of the locking plate 37retract the lining carrier 12 from the other brake members. Since theretraction stroke is limited by the distance locking plate 37 can movebefore it abuts washer 32, the rod 35 is retracted only a distanceequivalent to dimension X and therefore a new starting position isestablished for rod 35 and the lining carrier 12 in which the releaseclearance between the lining carrier and the other brake members isagain equal to dimension X.

The progressive relocation of the starting position of the rod 35 andthe lining carrier 12 in this manner does not change the maximumdeflection amplitude of the retractor spring 23. The retractor springdeflection amplitude remains substantially the same on every actuationfrom the time the brake is new until the lining is entirely worn out.

It can also be seen that as the starting position of the rod 35 isprogressively relocated and the effective length of the rod isincreased, the resetting spring 45 is compressed between the washer 51which moves to the right (as shown in FIG. 1) relative to sleeve 22 andthe plate 46 which maintains a substantially fixed position relative tosleeve member 22.

When the brake is released there is only the compressive force of spring45 tending to urge the rod 35 to the left (as shown in FIG. 1) and thefrictional grip of locking plate 37 is adequate to maintain rod 35 inany adjusted position. To replace the worn lining carriers, the positionof the rod 35 may be reset by merely straightening the locking plate 37as by an ordinary screwdriver 53 which may be inserted in the opening 44of the housing and turned to exert pressure against the flange 43 andear 42. When the locking plate 37 is straightened the gripping of therod 35 by the edges of the plate is reduced and the spring 45 will pushthe rod to the left (as shown in FIG. 1) into the sleeve member 22 tothe position shown by the bottom half of the rod from the position shownby the top half of the rod in FIG. 1. The lining carrier 12 maytherefore be removed by turning it in a circumferential direction sothat the enlarged head of the rod 35 may be removed from the slot 36 inthe lining carrier. This can be done without removing the retractorassembly or using any special tools. A new lining carrier 12 may then beinserted in the brake and slid into engagement with the rod 35. Thebrake is then ready to be used.

Depending on the size of the brake, one or a number of these retractorassemblies may be used in axially spaced position in the torque frame.

We, therefore, particularly point out and distinctly claim as ourinvention:

1. In a brake adjuster mechanism in which movement retractor rodattached to brake operating parts is axially movable inside a housingduring actuation and retraction of the brake parts, the retractor rodhaving its starting position in said housing on each actuation movementfixed by a tiltable plate in local engagement with such rod, thetiltable plate being biased to a position of engagement with such rod bythe biasing force of a retractor spring inside such housing, thetiltable plate being adapted for displacement to a position to releasesuch engagement with said rod when the axial displacement of such rodexceeds a predetermined distance to permit additional adjusting movementof said rod, the improvement which comprises a rod resetting spring insaid housing adapted for progressive deflection by the successiveincremental adjustment positions to which said rod is moved in saidhousing beyond said predetermined position, and an opening in saidhousing providing access to said tiltable plate from the exterior ofsaid housing for manually releasing the engagement of said tiltableplate from said rod so that the position of said rod relative to saidhousing is relocated by the biasing force on said rod exerted by saidrod-resetting spring.

EDWARD M-FLETCIER ,JF-i

(5/69) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3, 580,366 Dated My 25, 1971 Inventor(s) 0. Lucas Plaat and Donald F.Linn It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

Column '4, line 3, "t1" should read ---it---.

Column 6, line 6, "movement" should read -a---.

Signed and sealed this: 16M": day of May 1972.

(smL) Attesc:

ROBERT GOTTSCFTALK Attesting; Officer Commissioner of Patents

1. In a brake adjuster mechanism in which movement retractor rodattached to brake operating parts is axially movable inside a housingduring actuation and retraction of the brake parts, the retractor rodhaving its starting position in said housing on each actuation movementfixed by a tiltable plate in local engagement with such rod, thetiltable plate being biased to a position of engagement with such rod bythe biasing force of a retractor spring inside such housing, thetiltable plate being adapted for displacement to a position to releasesuch engagement with said rod when the axial displacement of such rodexceeds a predetermined distance to permit additional adjusting movementof said rod, the improvement which comprises a rod resetting spring insaid housing adapted for progressive deflection by the successiveincremental adjustment positions to which said rod is moved in saidhousing beyond said predetermined position, and an opening in saidhousing providing access to said tiltable plate from the exterior ofsaid housing for manually releasing the engagement of said tiltableplate from said rod so that the position of said rod relative to saidhousing is relocated by the biasing force on said rod exerted by saidrod-resetting spring.